Microscopic Origin of Magnetic Anisotropy in Au/Co/Au Probed with X-Ray Magnetic Circular Dichroism

Weller, D.; Stöhr, J.; Nakajima, Reiko; Carl, A.; Samant, Mahesh G.; Chappert, C.; Mégy, R.; Beauvillain, P.; Veillet, P.; Held, G. A.

doi:10.1103/physrevlett.75.3752

Cited by 379 publications

(246 citation statements)

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“…This change may be due either to the slight polarization of Au in the Co/ Au interface region or to the enhancement of the Co anisotropy, as observed in continuous and nanoparticulate films covered by Au. 21,22 A very slight decrease of the saturation field can be observed in the nanoparticulate Co films grown at 300 and 600°C. In the case of the polar loops shown in the right column of Fig.…”

Section: A Macroscopic Magnetic Propertiesmentioning

confidence: 87%

Morphology and capping effects in the magnetic and magneto-optical properties of nanoparticulate Co films

et al. 2008

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Magnetic and magneto-optical properties of Co films are studied as a function of the morphology and the capping layer. We show that the nanoparticulate structure of the Co films has a clear influence on the magnetic and magneto-optical properties of the system. Kerr measurements combined with x-ray magnetic circular dichroism provide evidence of a strong correlation between the collective magnetic behavior of the system and the individual atomic magnetic response. The influence of the magnetic nature of the capping layer ͑Al, Au, and Pt͒ is also analyzed. Polarized capping layers, such as Pt, magnetically couple the nanostructures and not only increase the effective anisotropy of the system but also enhance the atomic magnetic moment of Co and the global magneto-optical activity.

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Section: A Macroscopic Magnetic Propertiesmentioning

confidence: 87%

Morphology and capping effects in the magnetic and magneto-optical properties of nanoparticulate Co films

et al. 2008

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“…In the case of CrO 2 the local octahedral environment is distorted in the rutile structure; therefore the T z (index z is related to a local distortion) value could be significantly enhanced. Estimating now the spin moment, the 3d symmetry relation T z x + T z y + T z z = 0 has been applied, which has been published by Stöhr and König [31] and verified on a Au/Co/Au wedge by Weller et al [32]. Transferring this equation to the rutiletype unit cell yields 2 T z a + T z c = 0.…”

Section: Discussion 41 Spin Anisotropy and Magnetic Dipole Term T Zmentioning

confidence: 99%

Magnetic anisotropy of textured CrO 2 thin films investigated by X-ray magnetic circular dichroism

Goering¹,

Justen²,

Geissler³

et al. 2002

Applied Physics A: Materials Science & Processing

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Highly a-axis-textured CrO 2 films have been deposited on Al 2 O 3 (0001) substrates by chemical vapor deposition. CrO 2 has been found to have highly a-axis (010)-oriented columnar growth on a Cr 2 O 3 (0001) initial layer. The sixfold surface symmetry of the Cr 2 O 3 initial layer leads to three equivalent in-plane orientations of the a-axis-oriented CrO 2 unit cell. We report Cr L 2,3 X-ray magnetic circular dichroism data along the surface normal and at 60 • off-normal sample orientation. For a 60 • sample alignment, a strong increase of the projected orbital moment could be observed for unoccupied majority t 2g states using moment analysis. Therefore, the c axis is identified as the intrinsic magnetic easy axis of CrO 2 . In addition, a small spin moment and a very strong magnetic dipole term T z have been found. PACS 75.30.Cr; 75.30.Gw; 78.20.Lj; 78.70.Dm; 78.20.Bk IntroductionThe theoretically predicted 100% spin polarization at the Fermi energy, ε F , of CrO 2 makes it a promising material for magnetoelectronic devices [1][2][3]. According to Jullière's model, the magnetoresistance (MR) of a ferromagnet/insulator/ferromagnet tunnel junction depends on the spin polarization of the electrode material used [4]. The MR increases with increasing spin polarization of the ferromagnetic electrode material. Also, injection of spins from ferromagnetic metals into semiconductors may be allowed only for highly polarized metallic electrodes [5]. Additionally, transition-metal oxides like CrO 2 , high-temperature superconductors and colossal magnetoresistance lanthanum-based manganates have attracted a lot of theoretical interest due to the complex interplay between orbital, structural and electronic degrees of freedom. This has revived research on half-metallic ferromagnetic transitionmetal oxides, especially CrO 2 , in the past few years. Unfortunately, CrO 2 is metastable at room temperature and atmospheric conditions and typically a thin Cr 2 O 3 layer covers the CrO 2 surface. Methods like photoemission (PES), ✉ Fax: +49-711/689-1912, E-mail: goering@mf.mpg.de X-ray absorption (XAS) or X-ray magnetic circular dichroism (XMCD) spectroscopy could not easily be used for examination of basic properties of CrO 2 , because of their intrinsic surface sensitivity. Therefore, only a few experimental results on single crystals or epitaxial-grown thin films have been published. Nevertheless, spectroscopic methods are able to give quantitative information about intrinsic magnetic properties of CrO 2 . Experiment and resultsCrO 2 crystallizes in a tetragonal rutile-type structure, where chromium atoms form a body-centered tetragonal unit cell. Cr sites are octahedrally surrounded by oxygen atoms. The apical axis of the oxygen octahedra is oriented along the [110] ([110]) direction for the edge (bodycentered) Cr ions. The lattice parameters are a = b = 4.421 Å and c = 2.916 Å [6,7]. CrO 2 is a metastable Cr-oxide phase at room temperature, orders ferromagnetically at T C = 393 K and degrades above 400 K at ambient atm...

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“…In recent years, extensive work [10][11][12][13][14][15][16][17][18][19] on magnetic surfaces and thin films has shown that a lowering of the symmetry results in an increase of m L compared to bulk systems, where the d-state hybridization and the crystal field effectively quench m L . This effect gives rise to a variety of interesting phenomena, such as enhanced and perpendicular magnetic anisotropy [2,[12][13][14][15][16]19].…”

Section: Introductionmentioning

confidence: 99%

Magnetic anisotropy from single atoms to large monodomain islands of Co/Pt(111)

Gambardella

Rusponi

Cren

et al. 2005

Comptes Rendus. Physique

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By studying the magnetic behavior of self-assembled Co islands on a single-crystal metal surface, Pt(111), we show how the magnetic anisotropy evolves from isolated atoms to monolayer islands and films. Single Co adatoms are found to have a giant magnetocrystalline anisotropy energy of E a = 9.3 ± 1.6 meV/atom arising from the combination of partly preserved orbital moments (m L = 1.1 µ B ) and strong spin-orbit coupling induced by the Pt substrate. Combined scanning tunneling microscopy and X-ray magnetic circular dichroism experiments performed for differently sized small two-dimensional Co islands establish a clear connection between E a and m L , both quantities decrease sharply with the lateral coordination of the magnetic atoms. In accordance with this, Kerr magnetometry experiments, again performed in conjunction with scanning tunneling microscopy, reveal that the anisotropy energy of large two-dimensional Co islands is almost entirely determined by the relatively low number of perimeter atoms, having E a = 0.9 ± 0.1 meV/atom. These results confirm theoretical predictions and are of fundamental value the understanding of how the magnetic anisotropy develops in finite-size magnetic particles. Identification of the role of perimeter and surface atoms opens up new opportunities for engineering the anisotropy and the moment of a magnetic nanostructure. RésuméAnisotropie magnétique de l'atome isolé aux îlots monocouches de Co/Pt(111). En étudiant les propriétés magnétiques de particules de Co auto assemblées sur une surface d'orientation (111) d'un monocristal de Pt, nous montrons comment l'anisotropie magnétique évolue de l'atome isolé aux îlots monocouches et aux films ultraminces. Nous trouvons que les atomes de Co isolés adsorbés en surface ont une énergie d'anisotropie magnétocrystalline de E a = 9.3 ± 1.6 meV/atome provenant de la combinaison d'un moment orbital conservé (m L = 1.1 µ B ) et d'un fort couplage spin-orbite induit par le substrat de Pt. Des expériences combinées de microscopie à effet tunnel et de dichroïsme circulaire magnétique à rayons X, effectués sur des îlots de Co de petit taille établissent une connexion claire entre E a et m L , chacune de ces quantités décroissant rapidement avec la coordination latérale des atomes magnétiques. En conformité avec ceci, nous trouvons en employant la magnétométrie par effet Kerr et le microscope à effet tunnel que l'énergie d'anisotropie de grands îlots bidimensionnels de Co est presque entiè-rement déterminée par le nombre relativement faible d'atomes au périmètre, ayant E a = 0.9 ± 0.1 meV/atome. Ces résultats confirment les prédictions théoriques et sont d'un intérêt fondamental pour comprendre comment l'anisotropie magnétique se développe dans les particules magnétiques de taille finie. L'identification du rôle des atomes au périmètre et des atomes de surface ouvre de nouvelles opportunités pour l'ingénierie de l'anisotropie et du moment de nanostructures magnétiques. Pour citer cet article : P. Gambardella et al., C. R. Physique 6 (200...

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Microscopic Origin of Magnetic Anisotropy in Au/Co/Au Probed with X-Ray Magnetic Circular Dichroism

Cited by 379 publications

References 31 publications

Morphology and capping effects in the magnetic and magneto-optical properties of nanoparticulate Co films

Morphology and capping effects in the magnetic and magneto-optical properties of nanoparticulate Co films

Magnetic anisotropy of textured CrO 2 thin films investigated by X-ray magnetic circular dichroism

Magnetic anisotropy from single atoms to large monodomain islands of Co/Pt(111)

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